BERLIN — Violence against Syrian asylum seekers spiked over the weekend with police Sunday reporting three different attacks in which six Syrian refugees had to be treated for injuries. Attacks against asylum-seekers and migrant shelters have increased sharply in Germany in recent months as refugees surge into Europe seeking to escape war and poverty. Police in nearby Rostock said in a statement Sunday two Syrian men, who were not identified, were standing outside their shelter in Wismar on the Baltic Sea on Saturday night when a group of 20 persons approached them and started beating the refugees. The interior minister of Saxony, Markus Ulbig, sharply condemned the “cowardly and cold-blooded attack” and said a far-right motive was likely, the German news agency dpa reported.